Medical imaging techniques ranging from CT scans to myocardial perfusion imaging (or imaging of the heart), have become a regular part of medical diagnostics. Yet, according to a study published in this week’s issue of the New England Journal of Medicine, it isn’t yet clear whether the radiation necessary for these imaging procedures may actually be posing unnecessary harm.

Of 952,420 adults between the ages of 18 and 64, nearly 70% had at least one medical imaging procedure that required the use of radiation between July 2005 and December 2007. (The analysis did not include procedures that were used as part of treatment—radiation therapy to combat cancer, for example.) Across the population studied, it appeared that women overall tended to have higher cumulative doses of radiation during the study period, and that, generally, the older you were, the more radiation exposure you’d likely had in the three-year period. Yet, while older people had greater total exposure, the authors point out that 40% of women and 50% of men under the age of 50 were experiencing very high annual doses of radiation, in excess of 20mSv, or millisievert, the unit of measurement for doses of radiation. (To put that in context, the average dose of radiation for a mammogram is just 0.4mSv.) In the time frame studied, on average, individuals were exposed to nearly twice the radiation that they would normally encounter from the natural world.

The fact that exposure to even low-dose radiation has been linked with the development of certain types of cancer, including leukemia, underscores the importance of gaining a better understanding of the cumulative effect of low-grade radiation exposure during imaging procedures, the authors stress. Additionally, as each illness may be impacted differently by the information gained by imaging, it is important to conduct further research to determine when the benefits of the minor radiation exposure definitely outweigh the risks. And, on the flip side, future studies also need to clarify if and when patients are unlikely to benefit from imaging.

In the meantime, before more study results are available, the authors emphasize the importance of improving education—for doctors and patients alike—about the potential harm of low level radiation exposure. While current recommendations for radiation exposure call for keeping it “as low as reasonably achievable,” the authors point out that, maintaining this standard hinges upon treating physicians having a thorough understanding of not only the possible benefits, but also the risks posed by imaging techniques.